Movement (e.g., flexion and extension) of the natural human knee involves movements of the femur and the tibia. Specifically, during flexion and extension, the distal end of the femur and the proximal end of the tibia articulate relative to one another through a series of complex movements. Damage (e.g., trauma) or disease can deteriorate the bones, articular cartilage, and ligaments of the knee, which can ultimately affect the ability of the natural knee to function in such a manner. As a result, knee prostheses have been developed and implanted into surgically prepared ends of the femur and tibia.
Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. A typical knee prosthesis for a total knee replacement, for example, includes a tibial component or tibial tray coupled to the patient's tibia, a femoral component coupled to the patient's femur, and a bearing component positioned between the tibial tray and the femoral component and including a bearing surface to accommodate the condyles of the femoral component.
Orthopaedic surgeons use a variety of orthopaedic surgical instruments in performing joint arthroplasty. These instruments include, for example, provisional components, cutting blocks, drill guides, milling guides and other instruments. Provisional components are intended to be temporarily placed on the prepared bone surfaces prior to permanent fixation of the actual implant components. The provisional components are intended to mimic certain aspects of the permanent prosthetic joint in order for a surgeon to validate measurements, to test several different possible component sizes and shapes, and to evaluate alignment and kinematics by moving the joint with the provisional components in place. Hence, provisional components are aptly known as “trials”, and the procedure is known as “trialing.”
U.S. Pat. Nos. 9,028,501 and 9,095,356 (incorporated by reference herein in their entireties) illustrate and describe, among other things, tibial trial components. FIGS. 1-3 of the present application are taken from the drawings in those patents to describe trial components developed by the assignee of the present application.
FIG. 1 illustrates a provisional tibial base plate trial 10 that may be used in total knee arthroplasty to size and select the prosthetic components of a knee prostheses that will replace the patient's natural joint. It should be understood that a typical kit would include several sizes of tibial base trial plates 10 along with several sizes of tibial bearing insert trials, shown at 12 and 14 in FIG. 3.
As shown in FIGS. 1-2, the tibial base plate trial 10 includes a plate 16 having an upper surface 18, a lower surface 20, and an outer side wall 22 extending between the surfaces 18, 20. As described in U.S. Pat. Nos. 9,028,501 and 9,095,356, the plate 16 has passageways that permit the advancement of a keel punch and various other instruments into the proximal end of the patient's tibia. It should be understood that the illustrated plate may include all of the features disclosed in those patents.
The tibial base plate trial 10 includes a fastener that includes a button head 24 extending above (superior to) the level of the upper surface 18 of the tibial base plate trial 10. The button head 24 includes a reduced diameter neck 26 and a knob 28 secured to the neck 26. The knob 28 has a knurled outer surface that may be grasped by the surgeon to rotate the fastener about the longitudinal axis 30. The button head 24 also has a socket 32 defined therein, which is sized to receive a driver or other surgical tool to rotate the fastener about the axis 30.
As shown in FIG. 3, the prior art tibial trial system 34 also includes a number of tibial bearing trial assemblies. A tibial bearing trial assembly is disclosed in U.S. Pat. No. 8,968,412 entitled “TRIALING SYSTEM FOR A KNEE PROSTHESIS AND METHOD OF USE,” by Thomas E. Wogoman et al., which is incorporated herein by reference. Each illustrated tibial bearing trial assembly is a multi-piece assembly configured to assist the surgeon in selecting a size and configuration of a prosthetic tibial bearing component of the knee prosthesis. A tibial bearing trial may be assembled with one of a number of tibial bearing surface trials 36 and one of a number of a plurality of trial shims 38. Each bearing surface trial 36 has a different size and/or configuration, and each shim 38 has a different thickness. Because each shim 38 is configured to be secured to each bearing surface trial 36, the surgeon is able to assemble a tibial bearing trial of one size and configuration, evaluate the performance of that tibial bearing trial, and then modify the tibial bearing trial as necessary to determine intraoperatively the type and configuration of the prosthetic tibial bearing component to be implanted. It should be appreciated that tibial bearing trial may be a monolithic component, and the system 34 may include multiple tibial bearing trials of different sizes and configurations.
The system 34 may include one or more fixed bearing surface trials and one or more mobile bearing surface trials. Each of these types of trials may be provided as part of a cruciate retaining knee replacement system or as part of a posterior stabilized knee replacement system. For example, in embodiments where the bearing surface trial is embodied as a posterior stabilized trial, the fixed bearing surface trial may include a spine extending upwardly from the upper bearing surface of the trial.
In some cases, the condition of the patient's soft tissue, such as the collateral ligaments, may require use of a more constrained knee prosthesis. One type of constrained knee prosthesis is a hinged knee prosthesis, where the tibial insert and femoral component are connected by a hinge extended transversely through a spine on the tibial insert. In some hinged knee prostheses, it is desirable to allow “pistoning,” that is, to allow for the tibial insert to move superiorly and then return to its seated position during flexion and extension of the knee.
To produce an efficient prosthetic knee system that can be used with a patient population having a range of soft tissue conditions, it is desirable to utilize a trial kit that uses the tibial base plate trial such as the prior art plate trial 10 described above with tibial bearing insert trials that are usable in cases where a hinged prosthetic knee system will be used. In addition, it may be desirable to provide such a kit with multiple types of tibial bearing insert trials to allow the surgeon to trial different options intraoperatively.